/*
 *  Copyright 2013 National Institute of Advanced Industrial Science and Technology
 *  
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.sss.common.io;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.sss.mapreduce.DB;
import org.sss.mapreduce.DBFactory;
import org.sss.mapreduce.IOConfiguration;
import org.sss.mapreduce.StorageNode;

public class DBSet {
  private static Logger logger = LoggerFactory.getLogger(DBSet.class);
  private final Map<StorageNode, DB> dbMap = new HashMap<StorageNode, DB>();
  private int nRef;
  private final DBFactory dbFactory;
  private final IOConfiguration ioConf;

  public DBSet(DBFactory dbf, IOConfiguration ioConf) {
    this(dbf, ioConf, false);
  }

  public DBSet(DBFactory dbf, IOConfiguration ioConf, boolean isNotUsedByMe) {
    this.dbFactory = dbf;
    this.ioConf = ioConf;
    this.nRef = isNotUsedByMe ? 0 : 1;
  }

  public synchronized DB get(StorageNode node) throws IOException {
    assert nRef > 0: "referrence count is not positive.";

    DB db = dbMap.get(node);
    if (db == null) {
      DBFactory dbf = dbFactory;
      String factoryName = node.getDBFactory();
      if (factoryName != null) {
        logger.debug("factoryName: {}", factoryName);
        try {
          Class<? extends DBFactory> clazz = Class.forName(factoryName).asSubclass(DBFactory.class);
          dbf = clazz.newInstance();
        }
        catch (ClassNotFoundException e) {
          throw new IOException(e);
        }
        catch (InstantiationException e) {
          throw new IOException(e);
        }
        catch (IllegalAccessException e) {
          throw new IOException(e);
        }
      }
      db = dbf.getDB(ioConf, node.getHostName(), node.getPort());
      dbMap.put(node, db);
    }
    return db;
  }

  public synchronized void incRef() {
    nRef++;
  }

  public synchronized void close() throws IOException {
    if (--nRef == 0) {
      for (DB db: dbMap.values()) {
        db.close();
      }
      dbMap.clear();
      logger.debug("close db");
    }
  }
}
